I have heard it was safe to do but not sure.
Many of us don’t start adding cal/mag until flowering. Depends on what soil you are using.
Im using fox farms organic soil and my plants are getting big and need to be put on 12/12. My cal mag is being shipped now. They are not in horrible condition but they do need it
I use FF soils (Happy Frog) as well and have never needed to add cal/mag until flowering.
Cal/Mag won’t hurt just make sure it is low in N
I got cal mag plus by botanicare. Im not sure how much nitrogen is in it.
It has almost no nitrogen, which is good… You don’t want it to have too much during flower. It will prevent the plant from taking in what it needs. Besides, it will give your weed a nasty taste. (How do I know this?)
There’s a graphic someone put up about what nutes you need based on your ph runoff. I’ll see if I can find it. If someone else has it, please post.